Suddenly worse algae - need a stop gap to avoid a bigger bloom

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S

sparcel

Well-known member
May 25, 2022
57
San Jose, CA
Pool Size
21000
Surface
Plaster
Chlorine
Liquid Chlorine
I am unable to attend to pool for ~2 weeks and I'm getting algae suddenly - what do I do?

My main concern is that the algae might get much worse over the next two weeks and I might have a big problem when I can look at it again.

CYA ~40. I adopted the TFP chlorine levels in May when CYA was 50 and with chlorine in the 4-6ppm range (based on FAS-DPD) algae has stayed under control all summer. Only had to brush the walls of the pool a couple times to deal with very light algae. (Historically it would have been much worse.)

I've been keeping FC minimum closer to 4+ recently with my reduced CYA level and now have suddenly gotten much more algae on my pool walls and bottom (I don't know the two are related). It is a very thin coating on about 1/3 of the pool surfaces, but definitely there. The water is otherwise clear - except after I brush off the algae.

Another kinda odd thing is that my chlorine consumption has quickly dropped by about 65% down to only ~.7ppm per day over the last 2 weeks. This is my first year using a Stenner chlorine pump and tracking my FC so closely, but that seems like a faster drop off than I would have expected.

My phosphates have risen from <100 to 288 according to the pool store. (Yes, I know I should not trust their measurements and will soon get my own phosphate and CYA test kits).

My problem is I will be unable to attend to my pool for a couple of weeks and don't have the time to do a proper job of SLAMing or anything else. Others around the house cannot deal with it while I am busy.

I'm tempted to raise the FC level to something like 7 and hope for the best - but I don't know if it will help. (I do have a stenner pump so I can maintain the FC level automatically.)

I'm concerned about doing a shock or SLAM right now because I won't know how to stabilize the FC level without being able to attend to it in-person.

Note the pool store CYA results have been consistently 50 or lower all summer, so I doubt it is much higher than 50. And the most recent result was 35.
 
Here is what I would do:
1. Raise the pool to SLAM level (FC = 20 for a CYA of 50)
2. Set your Stenner pump to add 5 FC per day while you are gone
3. Order a proper test kit so it is here when you return, so you can properly SLAM and take care of your pool going forward.
 
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More info and a question

Info:
1. The weather was record breaking hot this last week - but, the pool temp stayed close to 84 whereas mid-summer it was around 89 and not much algae.
2. pH is 7.5.

Question:
Is there any merit in maintaining an FC level that is about double than normal range of 7.5% of CYA, but not full SLAM level? Or does that zone between the two have no value at all?
 
0.7 daily usage is really low and almost unheard of for a pool with algae. Normally a pool loses 3 or so FC per day, and 5 or more per day if it has algae.

On your question, I would certainly keep your FC at least elevated since you have algae. Keep in mind that you have algae because you kept your FC too low near the minimum levels. For your CYA of 50, the target range is 6-8 which is well above where you have been keeping yours. Before you go, I would still get your FC way up to SLAM level (20) and a way to supplement daily losses. If you are uncomfortable going out of town with it at 20, then I would be shooting for 10, or even better at 15.
 
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What about my question about your recommendation of adding 5ppm per day? I don't understand why, but I have been tracking my FC consumption pretty carefully and it has indeed been at .7 for the last couple weeks. It was more like 2.3 during most of the summer.
 
sparcel said:
What about my question about your recommendation of adding 5ppm per day? I don't understand why, but I have been tracking my FC consumption pretty carefully and it has indeed been at .7 for the last couple weeks. It was more like 2.3 during most of the summer.
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5ppm was a guesstimate. If you are really comfortable with the .7, then go with that, but I would take it up to SLAM level first.
 
sparcel said:
What about my question about your recommendation of adding 5ppm per day? I don't understand why, but I have been tracking my FC consumption pretty carefully and it has indeed been at .7 for the last couple weeks. It was more like 2.3 during most of the summer.
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I think the point that @JJ_Tex was trying to make was that you have algae and it will only get worse if you let your FC drop further. Keeping a replacement of 5ppm will offset the UV loss and some of he algae that is consuming it. If you wish to go lower, then that is your call. you just may have more to handle when you return in 2 weeks.
 
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I think I understand @JJ_Tex's point, and I very much appreciate the guidance. And I understand I certainly don't want my FC to drop below 7.5% of CYA. And given some uncertainty of my exact CYA I should allow a margin for this. The question is whether the ppm to add per day is at all related to the total FC level? i.e. does a higher level lose more per day?

In preparing to be gone I have been carefully working to understand my current FC consumption so-as to have my Stenner properly calibrated. The fact that the FC consumption dropped a lot suddenly ~2-3 weeks ago has made this harder because it had been very predictable during the summer at 2.3ppm/day. Nevertheless, even with clear skies I am confident that I am now at .7 - at least when targeting a total FC of 5.

(As to why consumption dropped suddently from 2.3ppm to .7ppm / day, my best guess is the this is because of the position of trees in the yard relative to the sun arc this time of year and the sun perhaps just dropped below an important threshold of height and is just not hitting the pool nearly as much as it did). The drop in pool temp would seem to indicate the same.
 

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sparcel said:
I think I understand @JJ_Tex's point, and I very much appreciate the guidance. And I understand I certainly don't want my FC to drop below 7.5% of CYA. And given some uncertainty of my exact CYA I should allow a margin for this. The question is whether the ppm to add per day is at all related to the total FC level? i.e. does a higher level lose more per day?

In preparing to be gone I have been carefully working to understand my current FC consumption so-as to have my Stenner properly calibrated. The fact that the FC consumption dropped a lot suddenly ~2-3 weeks ago has made this harder because it had been very predictable during the summer at 2.3ppm/day. Nevertheless, even with clear skies I am confident that I am now at .7 - at least when targeting a total FC of 5.

(As to why consumption dropped suddently from 2.3ppm to .7ppm / day, my best guess is the this is because of the position of trees in the yard relative to the sun arc this time of year and the sun perhaps just dropped below an important threshold of height and is just not hitting the pool nearly as much as it did). The drop in pool temp would seem to indicate the same.
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Please keep us informed upon your return. Have a safe travel.
 
Aside from my open question of whether the FC consumption is related to the total chlorine level, I have a question about @JJ_Tex thought that my habit of keeping FC at 4-6 it is not a good idea. Given my CYA of <=50, and my use of a Stenner dosing 3x / day, is it not ok to keep FC only a little above the minimum of 7.5% of CYA versus at the "Target" of 6-8 - so long as I don't allow it to dip below the minimum? My impression from other TFP threads was that being near the minimum was fine so long as I don't go below the minimum. Is that impression incorrect?

Given I have algae, obviously I am doing something wrong. Due to various circumstances I did allow FC to dip closer to 3 for a few days, and perhaps that triggered my algae issues. But it has been above 4 for the several days during which the algae became visible.
 
So yes, at a higher FC you will lose more chlorine.

The advice that has been given to you is sound, follow it.

Also I have a saying around here. All the experts run their FC hot. All the amateurs tend to skirt around the minimums. Guess who gets algae and who doesn’t.
 
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Given I have algae, obviously I am doing something wrong.
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Leaving a pool unattended for 2 weeks is quite problematic. Regardless of all you try, TFP pools need more attention than that.

Plan on SLAMing the pool on your return, but you will likely have to SLAM again the next time you leave it for a couple of weeks.

Your circumstances are what they are but TFP methods don't really do well for pools left alone for extended periods.
 
sparcel said:
Aside from my open question of whether the FC consumption is related to the total chlorine level, I have a question about @JJ_Tex thought that my habit of keeping FC at 4-6 it is not a good idea. Given my CYA of <=50, and my use of a Stenner dosing 3x / day, is it not ok to keep FC only a little above the minimum of 7.5% of CYA versus at the "Target" of 6-8 - so long as I don't allow it to dip below the minimum? My impression from other TFP threads was that being near the minimum was fine so long as I don't go below the minimum. Is that impression incorrect?
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Yes, but things happen like equipment breaks, bird poops in the pool, heavy bather loads, wind blows a bunch of stuff in the pool, etc. that can temporarily increase your chlorine consumption. Flirting with the minimum just doesn't give you the padding to handle those types of events, which is why we recommend the target ranges.

Also keep in mind that not all pools are the same. I've seen many people having to run a bit above the target due to things like poor circulation, a lot of trees dropping stuff in the pool, etc.

I tend to keep mine at the target range or a bit higher, just to help me sleep better at night knowing my pool can handle whatever is being thrown at it for the day.
 
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When we went out of town I put pucks in a floater. It made the chlorine go high (swg on but on a lower percentage) and were still partially there when we returned. I also wanted to raise cya. If your cya is truly low pucks might help along with adding the chlorine from your autofill. If you have any algae I would think you’d want your chlorine on the high end.
 
I was able to get a person staying at the house to test FC once, a week into my trip, and text me the results. I am able to remotedly control the schedule of my Stenner, so based on the FC test results I can make adjustments.

I do wish there was an Internet connected accurate, reliable, and inexpensive automated chlorine tester, or better yet, one that I could use to control my Stenner (again for a low cost). I'm not willing to spend $500+/year for this. $200-$300 a year might be ok if it was accurate and reliable.
 
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@duraleigh I’m curious, it seems you are suggesting a TFP is more of a problem to leave unattended for 2 weeks than other pools. What you are thinking in this regard? I would think they are all a problem. Without a Stenner or SWG I could see more of a problem for TFP pools, given that many such pool owners may not want to raise their CYA by using tablets while they are gone. Is another difference that a TFP pool takes a bit more effort to get into a stable TFP state, and you want to keep it there, whereas perhaps other pools already have a bit more continual chaos anyway?
 
it seems you are suggesting a TFP is more of a problem to leave unattended for 2 weeks than other pools.
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No. I am saying that NO pool should be left unattended for two weeks

Some sources will say, "Fill up the Tab feeder and walk away for as long as you like........we'll make your pool bulletproof".

TFP recognizes the difficulty of that approach and teaches and encourages a more hands-on approach.

So, if you compare this hands off procedure to TFP procedures, then, "Yes", TFP will be more troublesome.

The only problem with that is the sloppy approach simply doesn't work!
 
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